U.S. President Donald Trump says the trade relationship with Canada will only be "tweaked." The trouble is a little tweak in America can be a powerful thump in Canada.

The pleasure-pain imbalance is so severe that sometimes the Americans don't even realize it hurts.

The statistics prove it. Only 18 per cent of America's foreign trade comes to Canada. Fully 76 per cent of Canada's goes to the U.S.

So, it's best not to get too euphoric over Monday's White House meeting between Trump and Prime Minister Justin Trudeau. Genuinely encouraging as it was, real problems lie behind the friendly language.

Interim Conservative leader Rona Ambrose pointed out the Americans have major grievances with our beef imports and supply management in several areas of agriculture. There's also softwood lumber (that old thing).

Ambrose worries that Trump's aggressive deregulation and low-tax policy could make Canada uncompetitive. In that case, we could lose even if trade rules are untouched.

But she also had a kind word for Trudeau: "I've been on the record about some of the things Donald Trump has said about women."

"But this is a delicate situation here. I don't think it's going to help anyone in this country if the prime minister went to Washington and started a fight with the president."

Trudeau certainly didn't. His diplomatic performance, I thought, was masterful.

He didn't fawn over Trump, reach for his hand, look for an Obama style back-slap. The PM gave Trump no chance to offer a dismissive gesture. He kept a dignified emotional distance without being disrespectful.

Trudeau did a lot better, on balance, than British Prime Minister Theresa May, who almost started an uprising at home by casually inviting Trump for a visit.

Patrick Gossage, who was Pierre Trudeau's press secretary in the 1970s and 1980s, said, "(Justin) Trudeau's far too smart to have raised anything that would have annoyed Trump."

"He's well brought-up -- unlike his father, who would raise things with (Ronald) Reagan from time to time that Reagan did not like at all," Gossage told the CBC.

Reagan, who served as president from 1981 to 1989, once said after Trudeau urged him to press detente with Eastern Europe: "Damn it, Pierre, what do you want me to do?"

Trudeau needled earlier President Richard Nixon so artfully Nixon called him, in tapes released later, a "son of a bitch" and an "asshole." Trudeau rejoined: "I've been called worse things by better people."

NAFTA did not yet exist then. Now, trade is so vital that Justin Trudeau's key goal must be to protect it.

Both leaders made a great deal of the special relationship. If anything, Trump was more gracious than Trudeau. The president had no complaints about border security, trade irritants, or Canadian attitudes toward his many pronouncements.

He said to Trudeau, "On behalf of our country, it's an honour to be with you." At a joint press conference he called Canada "our great friend, neighbour and ally."

An event with female leaders, including TransAlta CEO Dawn Farrell, coincided with the announcement of a United States-Canada Council for Advancement of Women Entrepreneurs and Business Leaders.

The four-page communique summing up the day is a symphony of mutual support on trade, energy, border security, international alliances (including NATO and NORAD), the fight against ISIS and much more.

Most promising of all was the civil, respectful, bluster-free greeting Trump extended to both Trudeau and Canada.